The recent rapid directivity to digitization has led to increased opportunities of subjecting silver halide photographic materials to digital exposure. Along with such a trend, photographic color paper as a photographic material for color prints is desired with respect to suitability for exposure at a relatively high intensity for an extremely short time at the level of milli-seconds to nano-seconds and aptitude for scanning exposure.
There have been employed silver chloride emulsions or high chloride silver halide emulsions in color paper to achieve rapid processability. Further, it is commonly known that doping iridium compounds is effective to improve reciprocity law failure characteristics as a matter of properties of silver halide emulsions. There are disclosed high chloride silver halide emulsion grains having a high bromide region in the vicinity of the corners of the grains, as described in JP-A No. 64-26837 (hereinafter, the term JP-A refers to Japanese Patent Application Publication); high chloride silver halide emulsion grains in which a bromide-localized region is selectively doped with an iridium compound, thereby leading to superior latent image stability and reciprocity law failure characteristics, as described in JP-A No. 1-105940. There is also disclosed a method of forming a bromide-localized region by using silver bromide fine-grains doped with an iridium compound, as described in U.S. Pat. No. 5,627,020. However, neither of the foregoing methods was sufficient for improving latent image stability in the initial stage after exposure.
In digital exposure systems of the recent subject, it was proved that sufficient practical qualities were not achieved by only known techniques for improving latent image stability, in exposure suitability at a high intensity for an extremely short time. Techniques adaptable to such a digital exposure system include, for examples, chemical sensitization and spectral sensitization suitable for formation of a bromide-localized phase, as described in U.S. Pat. No. 5,691,119; and the use of a silver iodochloride emulsion, as described in European Patent Nos. 750,222 and 772,079.
However, it was proved in studies by the inventors of this application that the foregoing techniques for improving aptitude for digital exposure was not only insufficient for improving latent image stability but also resulted in marked deteriorated pressure resistance and pre-exposure storage stability of photographic materials. It is desired to immediately solve this matter.
JP-A No. 2001-188311 discloses a method for improving reciprocity law failure and coating solution stability, in which silver halide grains contain a bromide-rich or iodide-rich phase in the vicinity of the grain surface and introduction of such a rich phase is separated into two occasions, before and after addition of mercapto compounds. However, it was proved that using only this method was insufficient for improving storage stability of silver halide emulsions.
There were disclosed techniques for improving photographic performance such as sensitivity, fogging and reciprocity law failure by using silver iodochloride grains exhibiting iodide content decreasing from the grain surface in the direction of depth, as disclosed in JP-A No. 2002-174870, and high chloride silver halide grains having a maximum iodide content in the corners greater than that of the major faces, as disclosed in JP-A No. 2002-296718. However, there is further desired a technical improvement to achieve enhanced photographic performance and storage stability.
With regard to selenium sensitization, JP-A No. 5-66513 and U.S. Pat. No. 5,240,827 disclosed photographic elements comprising silver chloride grains containing a selenium compound on the grain surface, in which photographic performance, except for sensitivity was unclear and there was no description regarding gamma, a latent image and other performances required in photographic materials for print, so that it was difficult to provide a practical silver halide photographic material satisfying recently required performances. JP-A Nos. 5-313293, 9-5922 and 9-5924 disclosed silver halide photographic materials applying selenium or tellurium sensitization to silver chloride or high chloride silver bromochloride grains, in which improvement for performance such as latent image stability and coating solution stability were unknown and of which effects on sensitivity and gamma were insufficient to meet the recent demand for silver halide photographic material.
There were disclosed techniques for applying 8th group metal complexes containing an aqua ligand to silver halide grains, including a silver halide grain emulsion containing an iridium complex having halogen and aqua ligands and also having an iridium complex containing layer localized on the grain surface, as disclosed, for example, in JP-A No. 11-202440, and a silver halide emulsion containing high chloride silver halide grains occluding an iridium complex having an aqua ligand, as disclosed in JP-A No. 2001-356441. There were also disclosed techniques for applying 8th group metal complexes containing an organic ligand to silver halide grains, including a silver halide emulsion containing high chloride silver halide grains occluding a six-coordinate complex of metals other than iridium and an iridium complex containing a thiazole or substituted thiazole ligand, as disclosed in U.S. Pat. No. 6,107,018, and a silver halide emulsion containing high chloride silver halide grains occluding an iridium complex containing an aqua or thiazole ligand and an iridium complex containing a halogen ligand, as disclosed in JP-A No. 2002-162708. However, the foregoing techniques were insufficient to meet recent requirements for enhanced sensitivity, latent image stability and digital exposure suitability.
Further, there was also disclosed introduction of dislocation lines into silver halide grains, for example, JP-A No. 2001-255613 disclosed a silver halide tabular grain emulsion containing dislocation in the fringe portion of (111) major faces, JP-A No. 2003-15244 disclosed a silver halide tabular grain emulsion comprising (111) major faces having epitaxial junctions in the corner portion and containing dislocation lines in the epitaxial portion, JP-A No. 11-218866 disclosed a silver halide tabular grain emulsion containing dislocation lines in the fringe portion or in the vicinity of the corner, and JP-A Nos. 2000-241922 and 2001-133921 disclosed a silver halide emulsion comprising regular crystal grains containing dislocation lines. However any one of the foregoing disclosures concerns techniques of silver halide emulsion mainly comprised of silver iodobromide, intended for color negative photographic materials and there was no disclosure regarding introduction of dislocation lines into silver halide regular crystal grains mainly comprised of silver chloride.